Ungulates (Deer, Elk, Moose)

Damage Assessment

White-tailed deer, Odocoileus virginianus

Ungulate damage to various agricultural, forestry, and ornamental crops caused by feeding, trampling, and antler rubbing is an increasing problem. Deer browsing in winter on buds of apple and other fruit trees can reduce yields the following year (Austin and Urness 1989) or adversely alter the growth pattern of tree limbs (Harder 1970). Similar browsing on nursery plants and in Christmas tree plantations can reduce or eliminate their market value (Scott and Townsend 1985). Browsing of hardwood saplings and young fir trees in regenerating forests can reduce growth rates, misshape trees, and even cause plantation failures (Crouch 1976, Tilghman 1989). Damage to trees caused by antler rubbing can be severe (Scott and Townsend 1985). Small trees (1/2 to 1 inch [1.6 to 2.5 cm] in diameter at 6 inches [15 cm] above ground) with smooth bark, such as green ash, plum, and cherry, were preferred for antler rubbing by white-tailed deer in an Ohio nursery (Nielsen et al. 1982).

Objective estimates of economic loss from ungulate browsing and rubbing in orchards, nurseries, and reforestation projects are difficult to obtain. Losses in yield or tree value may accumulate for many years after damage occurs and vary with other stresses, including rodent damage, inflicted on the plants. In Ohio, growers reported average losses to deer in 1983 of $82 per acre ($204/ha) for orchards, $89 per acre ($219/ha) for Christmas tree plantings, and $108 per acre ($268/ha) in nursery plantings (Scott and Townsend 1985). Losses apparently are in the millions of dollars annually in some US states (Black et al. 1979, Craven 1983b, Connelly et al. 1987).

Deer also feed on various agricultural crops, especially young soybean plants and ripening ears of corn. Hygnstrom and Craven (1988) estimated a mean loss of 2,397 pounds of corn per acre (2,680 kg/ha) for 51 unprotected corn fields in Wisconsin. Yield reductions in soybean fields are most severe when feeding occurs during the first week of sprouting (DeCalesta and Schwendeman 1978). Elk in some areas raid hay-stacks and cattle feedlots (Eadie 1954).

Damage Identification

Ungulates do not have an upper set of incisors. Thus, twigs or plants nipped by these hoofed species do not show the neat, sharp-cut edge left by most rodents and lagomorphs, but instead show a rough, shredded edge, and usually a square or ragged break. Pearce (1947) observed that deer in the Northeast seldom browse higher than 6 feet (1.8 m) from a standing position, but are able to reach up to 8 feet (2.5 m) by rearing up on their hind legs. Elk and moose browse to a height of about 10 feet (3 m). Deer seldom browse on branches more than 1 inch (2.5 cm) in diameter. Moose and elk will gnaw the bark of aspen trees. When male ungulates rub the velvet from their antlers, the scarring is generally confined to the trunk area up to 3 feet (1 m) high (Pearce 1947).

Summary of Damage Prevention and Control Methods

Exclusion

Fences provide the most consistent control: 8-foot (1.4-m) woven wire fence, Tensar®, or wooden snow fence around small plots or haystacks.

Several configurations of electric fences are available: vertical five, seven, or nine-wire, slanted seven-wire, single strand, and others.

Individual tree protectors include: woven wire or plastic cylinders.

Cultural Methods and Habitat Modification

Plant trees and shrubs that are resistant or less susceptible to deer damage. Harvest crops as early as possible to reduce vulnerability.

Lure crops may divert deer away from areas that are susceptible to damage. Habitat modification generally is not recommended.

Frightening

Gas exploders, pyrotechnics, gunfire, or tethered dogs provide temporary relief.

Repellents

A wide variety of commercial formulations is available: area repellents--applied near plants to be protected, repel by smell;

contact repellents--applied directly to plants to be protected, repel by taste; a few, such as Deer-Away, possess characteristics of both groups.

Toxicants

None are registered.

Live Capture

Deer can be live-trapped or chemically immobilized for removal by professional biologists--useful only in special cases, such as city parks.

Shooting

Sport hunting can reduce deer populations and should be encouraged.

Some states may issue permits to shoot deer outside normal sport hunting seasons.